This invention relates generally to fuel filters employed in connection with internal combustion engines. More particularly, the present invention relates fuel filters having a replaceable cartridge for removing foreign particles and/or separating water from fuel of the fuel supply system of an internal combustion engine.
It has long been recognized that trouble free operation of an internal combustion engine requires some form of filtering of the fuel consumed by the engine. In particular, the absence of high standards of quality control in diesel fuel supplies dictates that an effective fuel filter be incorporated into the fuel supply system for a diesel engine. It is not uncommon for diesel fuel to have significant quantities of abrasive particles and water. The abrasive particles present the potential for permanent damage to components of the fuel injection pump. The abrasive particles can also adversely effect the performance of the pump by destroying the ability of the fuel injection pump to precisely meter and deliver fuel at high pressures. The presence of water in the diesel fuel supply can cause rusting of engine components, and during freezing conditions, can result in interruption of the fuel injection system and/or seizure of moving components.
Diesel fuel also contains a waxy constituent which precipitates as wax crystals when the fuel temperature drops below a characteristic "cloud point". In cold weather conditions, the precipitating wax crystals can rapidly plug a fuel filter and thereby cut off fuel delivery to the internal combustion engine.
A number of conventional fuel filters perform the dual function of removing particulate material from the diesel fuel and separating water from the fuel. In addition, conventional fuel filter units or fuel conditioners frequently employ heaters to prevent wax crystal formation. Conventionally, the fuel filters employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage.
In practice the filter cartridge requirements may vary depending upon such characteristics as the type and make of the internal combustion engine, the specific applications for which the engine is employed, the climate in which the combustion engine is operated and/or regional characteristics as to the quality of the fuel supply. The filter cartridges thus commonly vary as to axial dimensions, capacity and filter media qualities.
One of the problems which is frequently encountered in connection with replacement of the filter cartridge is insuring that the replaced cartridge is compatible with the filtering requirements for the fuel system. Because numerous types and qualities of filter cartridges may dimensionally conform to the base of a given filter assembly, the replacement filter cartridge frequently does not comply with the specifications for the filter assembly, thereby jeopardizing the integrity of the fuel filtering system. The replacement with an incompatible filter cartridge can have very serious effects on the operation of the internal combustion engine and may also be unnecessarily expensive when a less costly cartridge is fully suitable. Frequently, either the owner or the maintenance personnel servicing the internal combustion engine are totally unaware of the replacement filter cartridge specifications and requirements and unknowlingly jeopardize the integrity of the filtering system. There are also instances where inferior or improper replacement filter cartridges are intentionally installed without the knowledge of the owner or operator of the vehicle.
U.S. Pat. application Ser. No. 372,645 filed on June 28, 1989 and U.S. Pat. application Ser. No. 404,849 filed on Sep. 8, 1989, both of which applications are assigned to the assignee of the present invention, discloses a fuel filter assembly which employs a base mounting a disposable filter cartridge. The cartridge includes a dual stage filter system wherein fuel flows generally axially to a primary filter element for removing particulate matter and for coalescing water droplets and generally axially to a second filter stage which functions as a water barrier. The cartridge includes an endcap which is secured to the cartridge housing by a rolled seam. The endcap contains an annulus defining a plurality of slots adjacent the rolled seam structure for allowing fuel communication between the cartridge and the filter base. The base forms a sealing ring which engages the lip and the endcap of the cartridge to seal the cartridge with the base.